Abstract: When optimized biological enzyme was injected into the underground reservoir, a series of metabolites such as acid and gas, etc. were produced after in situ reproduction for a certain period of time. These metabolites could change the physicochemical properties of formation and reservoir crude oil so as to enhance oil recovery. Aiming at the characteristics of high alkali, high salt, high mineral degree of Huoshaoshan and Beisantai low permeability oilfield, the reservoir adaptability experiment showed that biological enzyme could grow in harsh conditions normally. The bio enzyme could effectively enhance oil recovery through the bio enzyme core oil displacement experiment. The bio enzyme flooding experiments in oil well and water well have good effect of oil recovery.